The present invention relates to methods and devices for tissue sampling, and more specifically to improved biopsy instruments and methods for acquiring subcutaneous biopsies and for removing lesions.
It is often desirable and frequently necessary to sample or test a portior tissue from humans and other animals particularly in the diagnosis and treatment of patients with cancerous tumors, premalignant conditions, and other diseases or disorders. Typically, in the case of cancer, when the physician establishes by means of procedures such as palpation, x-ray, or ultrasound imaging that suspicious circumstances exist, a biopsy is performed to determine whether the cells are cancerous. Biopsy may be done by an open or percutaneous technique. Open biopsy, which is an invasive surgical procedure using a scalpel and involving direct vision of the target area, removes the entire mass (excisional biopsy) or a part of the mass (incisional biopsy). Percutaneous biopsy, on the other hand, is usually done with a needle-like instrument through a relatively small incision, blindly or with the aid of an artificial imaging device, and may be either a fine needle aspiration (FNA) or a core biopsy. In FNA biopsy, individual cells or clusters of cells are obtained for cytologic examination and may be prepared such as in a Papanicolaou smear. In core biopsy, as the term suggests, a core or fragment of tissue is obtained for histologic examination which may be done via a frozen section or paraffin section.
The type of biopsy utilized depends in large part on circumstances present with respect to the patient, and no single procedure is ideal for all cases. However, core biopsy is extremely useful in a number of conditions and is being used more frequently by the medical profession.
Two types of image guided percutaneous core breast biopsy instruments are presently available. One such instrument is a spring-powered single-use device, such as the BIOPTY(copyright) gun, available from C. R. Bard, Inc. Such a gun is shown and described in U.S. Pat. Nos. 4,699,154 and 4,944,308, as well as in U.S. Reissued Pat. No. Re. 34,056, all of which are herein expressly incorporated by reference. These devices are useful because of their inexpensive construction, enabling them to be economically used for only a single patient, and because they are lightweight and easy to use. However, they also have disadvantages. An important disadvantage is that the small core size makes it necessary to accurately place the needle when sampling small lesions. To sample a lesion thoroughly, many separate insertions must be made. Each time a new sample is taken, the device must be removed, and the breast or organ must be punctured again upon re-insertion of the device. This action is tedious and time consuming.
A further disadvantage of such single-use guns is the needle typically used in such a device, e.g. the True Cut(copyright) needle manufactured by Travenol Laboratories. This needle optimally allows a roughly cylindrical shaped sample of tissue, termed a xe2x80x9ccorexe2x80x9d, to be obtained from a pointed, side cutting device, percutaneously, and comprises a pointed inner stilette with a side-facing notch to receive tissue near its distal pointed end and an outer, sharpened sliding cannula. In operation, once the lesion is targeted, the inner stilette is thrust into the organ or lesion of interest. Tissue passively prolapses into the side facing notch and the outer cannula is rapidly advanced, thereby severing the sample of tissue contained within the notch. Unfortunately, the True Cut(copyright) needle is rough on organs and lesions, often only obtaining small fragments of tissue, and is quite operator dependentxe2x80x94some individuals are good at operating the device and some are not. It also is tissue selective, meaning that the piercing stilette and sliding cutter can xe2x80x9cpush awayxe2x80x9d the lesion of interest, particularly in situations where a relatively large lesion is surrounded by much softer tissue (i.e. fat).
The second type of image guided percutaneous core breast biopsy instrument currently available is a vacuum-assisted automatic core biopsy device. One such successful biopsy gun is shown and disclosed in related parent application Ser. No. 08/217,246, filed on Mar. 24, 1994, which is commonly owned by the assignee of the present application and is herein incorporated by reference. This gun has the capability to active capture tissue prior to cutting the tissue. Active capture allows for sampling through non-homogeneous tissues, meaning that the device is equally capable of cutting through hard and soft tissue. The gun also includes means to direct and position the cutting chamber in arbitrary positions about and along its longitudinal axis, means for rapid and atraumatic removal of an arbitrary number of core samples with only a single needle insertion into the body and organ, and means for coding and decoding the location from which the samples were obtained. Together, these capabilities allow for more complete sampling of large lesions and for the complete removal of small lesions. This type of instrument has been very successful in permitting the obtainment of a plurality of tissue samples from different locations with only a single needle insertion, as well as in obtaining high quality samples in a manner which does not require direct handling of the samples by the operator. However, it does not operate equally well in all procedures and in all bodily environments. For example, instrument performance and success often varies dependent upon the type of body tissue being sampled; i.e. relatively fatty or relatively hard.
What is needed then, are innovations for improving the quality and completeness of the tissue sample obtained using a single-use core biopsy instrument, as well as constructional improvements and variants with respect to the active capture type of instrument which will permit it to operate with maximum efficiency and to operate equally well in all tissue environments.
This invention addresses the aforementioned needs by providing a number of important new features and innovations for the active capture type of biopsy instrument which each collectively or singly contribute to improved and more versatile operation. For example, such innovations include a molded tissue cassette housing, permitting easy and inexpensive fabrication while also permitting the handling and viewing of multiple tissue samples without physical contact by the instrument operator. The housing is interconnected with the piercing needle using a thumbwheel which permits the needle to rotate relative to the housing, thereby preventing the vacuum tube from wrapping about the housing. Several variant vacuum port embodiment are disclosed, each of which have advantages in certain tissue environments. Also disclosed is a method for backflushing biological debris from the instrument which builds up after repeated sampling procedures, without removing the instrument from the selected tissue location.
With respect to the single-use type of biopsy instrument, several tissue capture embodiments are disclosed for improving the capture process, so that complete and well preserved samples are obtained. Many of these embodiments are also applicable for use with the active capture instrument type.
More particularly, in one aspect of the invention, a biopsy instrument is provided which comprises a housing and a needle assembly, wherein the needle assembly includes a tubular piercing member having a distal pointed end and a laterally positioned tissue receiving port proximate to the distal pointed end which opens into a tissue sample chamber. The tubular piercing member is rotatably attached to the housing and held in an axially fixed position within a selected tissue mass. The needle assembly further includes a cannular cutting member adapted to coact with the tubular piercing member to cut a tissue sample from the tissue mass. The tissue sample is transported to a proximate end of the tubular piercing member by the cutting member as it is withdrawn proximally along the tubular piercing member. An elongate knock-out pin is disposed coaxially within the tubular piercing member and the cannular cutting member for the primary purpose of dislodging the tissue sample from the cutting member at a predetermined location as the cutting member is withdrawn.
Surprisingly, the inventors have found that preferably, in order to minimize tissue clogging of the cutter, the knock-out pin should have an effective diameter or cross-sectional area of at least 0.030 inches, and the ratio of the effective diameter of the knock-out pin to the internal diameter of the cannular cutter should be at least approximately one-half.
In another aspect of the invention, a biopsy instrument includes an elongate hollow outer piercing needle having a lumen, a sharpened distal end for piercing tissue, and a lateral opening located proximal to the sharpend distal end for receiving a portion of a tissue mass positioned adjacent to the lateral opening. Also included are an elongate inner cutting cannula having a lumen, which is disposed coaxially and slidably within the outer piercing needle. The inner cannula has a sharpened distal end for cutting the portion of tissue protruding into the lateral opening of the outer piercing needle when the inner cannula slides distally past the lateral opening. This causes the portion of cut tissue to be deposited within the inner cannula proximal to the distal end. A vacuum generator generates a vacuum pressure which fluidly communicates with the lateral opening through the inner cannula lumen. In such an embodiment, it is often desirable to prevent the tissue sample from migrating proximally through the cutting cannula lumen, so an inventive tissue stop device is disposed in the lumen of the inner cannula which has a structure, preferably a corkscrew portion of a linear wire, disposed proximally of the lateral opening. This structure sufficiently obstructs the lumen so that the tissue sample cannot migrate proximally past it.
In yet another aspect of the invention, a biopsy instrument includes an outer hollow cannula having a distal end portion which comprises a plurality of leaftlets. Each leaflet has a proximal end which is hinged to the outer cannula wall and a distal end, and are each biased to pivot about their hinges to a closed position wherein the distal ends of the leaflets contact one another. The instrument further includes an inner hollow cannula, and at least one of the inner and outer cannulas is slidable relative to the other cannula, so that first the inner cannula may be extended distally with respect to the outer cannula to force the leaflets to an open position, and to cut and contain a tissue sample, and then the outer cannula may be extended distally with respect to the inner cannula sufficiently so that the leaflets clear the inner cannula and snap closed about their hinges, thereby severing the tissue sample and containing it within the inner cannula.
In a further aspect of the invention, a biopsy instrument has an outer hollow cannula having a sharpened distal end portion and an inner hollow cannula having a distal portion which is biased to expand radially at its distal end. At least one of the cannulas is slidable relative to the other cannula, so that fit the inner cannula may be extended distally with respect to the outer cannula, such that the inner cannula distal portion expands radially to capture a tissue sample. Then the outer cannula may be extended distally with respect to the inner cannula sufficiently so that the distal end portion of the inner cannula is forced by the outer cannula to close about and sever the tissue sample, thereby containing the sample within the inner cannula. The distal portion of the inner cannula may comprise, for example, either an alligator tip having a pair of hinged jaws which are biased to expand radially, or a plurality of hooked extractors.
Still another aspect of the invention involves a method for flushing debris form a biopsy instrument, which includes an outer piercing needle having a laterally positioned tissue receiving port which opens into a tissue receiving chamber and an inner cutting cannula having an axial lumen and a sharpened distal end, which is disposed coaxially and slidably within the outer piercing needle. Further included in the biopsy instrument is a vacuum lumen disposed beneath the tissue receiving port which further comprises at least one fluid communication port disposed distally of the distal end of the inner cannula when the inner cannula is in its fully advanced position. The inventive method includes the steps of advancing the inner cannula of the instrument so that it extends distally sufficiently to completely close off the tissue receiving port and then injecting a pressurized fluid through one of the inner cannula and the vacuum lumens, so that the fluid flows through the fluid communication port and into the other one of the two lumens, from which the fluid returns to its source, thereby flushing accumulated debris from the biopsy instrument.
The invention, together with additional features and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying illustrative drawing.